Apparatus for weathering coated test panels



INVENTOR. sr PH? E. NEWFIELD A TORNEYS S. E NEWFIELD Filed June 5, 1968APPARATUS FOR WEATHERING COATED TEST PANELS March 17, 1970 United StatesPatent 3,500,682 APPARATUS FOR WEATHERING COATED TEST PANELS Stephen E.Newfield, 4309 Fairway, Los Alamos, N. Mex. 87544 Filed June 5, 1968,Ser. No. 734,751 Int. Cl. G01n 17/00 US. Cl. 73-150 7 Claims ABSTRACT OFTHE DISCLOSURE Panels coated with a protective, anti-corrosive materialto be tested are mounted in the top portion of a cabinet which alsocontains a plurality of fluorescent lamps and a reservoir filled withWater. The water is heated to fill the container with a water vapor andthe fluorescent lamps energized to radiate ultra-violet light onto thetest surfaces of the panels. By separately controlling humidity andradiation, weathering is substantially accelerated and environmentalconditions of use can be approximated.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates to testapparatus and, in particular, to apparatus for weathering panels coatedwith anti-corrosive protective coatings.

Several accelerated weathering devices presently are in use, theprincipal ones being the weatherometer and the salt spray cabinet. Mostweatherometers essentially are variations on one general arrangement inwhich the test panels are placed on the inside of a large drum whichrotates about an ultra-violet light source disposed in the center. Thesource may be a carbon are or a xenon lamp, the panels also beingrotated through a section in which they are wetted by a water spray.Such an arrangement appears to be seriously limited in its ability toprovide a corrosive environment and in addition it requires extensivemaintenance, such as the changing of carbons, etc. The apparatus also isrelatively expensive, requires high power sources and special plumbingattachments for its supply of de-ionized water.

The salt spray type of accelerated weathering apparatus utilizes acorrosive environment of moisture and salt, these devices being closedchambers utilizing an atomizer to introduce the salt solution as a finemist. Aside from the fact that sunlight is not simulated, thesearrangements also require extensive maintenance to replenish the saltsolutions and to charge the units with compressed air.

OBJECTS OF THE INVENTION It is therefore a principal object of thepresent invention to provide Weathering apparatus capable ofsignificantly accelerating the weathering effects, the apparatus beingrelatively small, inexpensive, and easily maintained.

Other objects and their attendant advantages will be considered in thedetailed description which is to follow.

SUMMARY OF THE INVENTION The objects of the invention are achieved byemploying a cabinet preferably formed of anti-corrosive material, thecabinet being provided in its upper portion with means for mounting thetest panels. A reservoir is formed in the lower portions of the cabinetand heater means provided to heat the water contained in the reservoir.When heated, a water vapor fills the cabinet and, due to the temperaturegradient between the interior and the exterior of the cabi- 3,500,682Patented Mar. 17, 1970 net, the water vapor condenses on all interiorsurfaces, including the test panels. An elongate ultra-violet lightsource, such as several fluorescent lamps, extend from one end of thecabinet to the other medially of the cabinet. Preferably, thearrangement of the fluorescent lamps is such that radiation from theselamps is evenly distributed over the test surface areas of the panels.Cycle control means permits the light and the heat to be regulated inany desired manner. For example, conditions can be established forpromoting maximum weathering acceleration, or, if desired, the controlscan be regulated as to simulate the particular environmental conditionsanticipated in the use of the coatings.

BRIEF DESCRIPTION OF THE DRAWING A preferred embodiment of the inventionis illustrated in the single figure of the accompanying drawing which isa somewhat schematic perspective view of the cabinet and itsincorporated components.

DESCRIPTION OF THE PREFERRED EMBODIMENT The operative elements of theinvention are contained in or mounted on cabinet 1 formed of side walls2, end walls 3, a bottom wall 4, and a top which, as may be seen in thedrawing, is formed of a center beam 6 supported by end walls 3 and byabbreviated canted ledge portions 7. Panels 8, which are in the form ofrectangular plates, are mounted side by side to complete the formationof the top wall and to provide an enclosed container structure.Preferably, the panels are supported by ridges 9 providing an abutmentagainst which the panels rest.

As already indicated, the principal function of the cabinet is to permitan accelerated weathering of test panels which have been coated with aprotective coating to be tested. Particularly coaings would be thevarious anticorrosive pains to be used on ships or in other corrosiveenvironments. For test purposes, one surface of the panels is coatedwith the material and the panels then positioned on the container sothat the coating surfaces face inwardly.

Accelerated weathering is accomplished by exposing the test panels toultra-violet light and to moisture. The moisture is derived from asupply of water 11 contained in a reservoir portion of container 12,this portion being formed principally by bottom wall 4 of the cabinet.Beneath reservoir 12 is a heating unit 13 which, most suitably, utilizesa coil heater to raise the water temperature sufficiently to cause theinterior of the container to become filled with a water vapor. Themoisture for the test panels is supplied by the water vapor whichcondenses on the test panels due to the temperature gradient between theinterior of the casing and its exterior.

Weathering also includes exposing the test panels to an ultra-violetlight source that simulates natural sunlight, the source being threefluorescent lamps 14 mounted in a triangular arrangement in end Walls 3so that the lamps extend throughout the length of the container from oneend to the other. It is most desirable to provide an even distributionof the ultra-violet radiation and to achieve such a distribution, thetriangular arrangement of the lamps matches the triangular shape of thetop of the container.

Both the fluorescent lamps and the heater are electrically energizedthrough a power line 16 provided with a plug by means of which the powerline can be coupled into conventional line sources. Power for the lampsis supplied through a timer switch 17, a starter and ballast unit 18 anda socket fixture 19. The fluorescent lamps most suitably are of thegermicidal type capable of emitting intense ultra-violet light, suchtypes being filled with a mercury vapor or a vapor of some othercomposition capable of breaking down into a self-maintainingdis charge.A variety of these lamps are available commercially. Starter and ballastunit 18 also is a commercial item customarily used with fluorescentlamps, the starter, when energized, opening to provide high voltageacross the electrodes causing the vapor to break down. The ballastportion of unit 18 is employed to limit the current to a safe valuesince the self-maintaining discharge is not inherently self-limiting.Timer switch 17 may be any conventional available switch such as thecommon types operating on a clock mechanism. Its purpose is to controlthe light cycle by shutting ofl? line power after a predetermined timeinterval. The switch utilizes a settable dial 21 permitting the operatorto set the light cycle according to a predetermined testing program.

Heating unit 13, which, if desired, could be an immersion type, derivespower from the line source and the power is applied through anothertimer switch 22 having a dial 23 similar to switch 17. The circuit alsoincludes a thermal switch 24 disposed in the interior of container 1.The thermal switch, which is commercially available in many varieties,is employed for the obvious purpose of automatically regulating theinterior temperature of the system. It provides closer temperaturecontrol by automatically interrupting the power supply when apredetermined temperature has been reached.

The operation of the cabinet should be apparent from the previousdescription. Panels 8 initially are prepared by coating one side surfacewith the protective coating to be tested, and, as contemplated, thiscoating usually will be of an anti-corrosive nature. The panels are thenplaced in position to enclose the top of the cabinet and provide anenclosed structure capable of providing a temperature diflerentialbetween the interior and exterior surfaces. Depending upon the naturalconditions which the testing is intended to simulate, power then isapplied to either or both the lamps and the heater. Radiation from thelamps simulates sunlight, while the vapor rising from the heated waterprovides the corrosion-promoting humidity by condensing on the coatedsurfaces of the panels. Settingpf the timers limits the application ofthe radiation and moisture in accordance with the test program.Obviously, no ideal program will simulate all conditions and it is forthis reason that the unit is provided with its flexibility. For example,if the ships surface on which the tested coating is to be applied is asurface which rarely is exposed to direct sunlight, the operation of thefluorescent lamps can be limited or eliminated entirely.

The particular advantages of this apparatus aside from its flexibility,lies in its compactness, low expense and particularly in its ability tosignificantly accelerate the weathering of the panels. In use, 'suchcabinets increase the weathering by a factor of about three as comparedwith more conventional weatherometers. Other advantages are that theapparatus avoids the need for compressed air atomizing devices andexpensive plumbing arrangement and that the water providingtheweathering moisture can be ordinary tap water. Such simplificationsmaterially reduce maintenance and minimize shut-down time.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that the invention may be practiced otherwise than asspecifically described.

What is claimed is:

1. Apparatus for promoting a controlled weathering of coated testpanels, said apparatus comprising:

an anti-corrosive cabinet,

stationary means for mounting a test panel in the upper portion of saidcabinet, reservoir means formed in the lower portion of the cabinet andadapted to contain a water supply, means for heating said water toproduce water vapor, said test panel having an exterior surface subjectto the environment outside said cabinet for inducing the formation of acondensate on a surface of said panel interiorly the cabinet, anelongate ultra-violet radiation source extending medially through saidcabinet, means for energizing said radiation source, and means forseparately and independently controlling the operative cycles of saidradiation source energizing means and said water heating means, saidpanel mounting means exposing a coated surface area of said panel tosaid radiation and water vapor and said mounting means being arrangedrelative to said radiation source for prompting a uniform distributionof the radiation on said exposed surface area. 2. The apparatus of claim1 wherein said radiation source is formed of a plurality of fluorescentlamps.

3. The apparatus of claim 2 wherein said cabinet is an elongatestructure having top, bottom, side and end walls,

said top being formed with means for mounting a plurality of test panelsside-by-side for providing a top enclosure for the cabinet so that onesurface of each panel is subject to the environment outside said heatedcabinet to induce the formation of a condens-ate on a surface of eachpanel inside the cabinet. 4. The apparatus of claim 3 further includingstarter and ballast means for said fluorescent lamps.

5. The apparatus of claim 4 wherein said radiation source energizingmeans and said water heating means include a power line, and

said control means includes separate timer switches electricallycoupling said energizing and heating means separately to said powerline. 6. The apparatus of claim 5 wherein said control means furtherincludes thermally-responsive switch means electrically coupled betweensaid water heating means and its timer switch,

said thermal switch being carried internally of said cabinet. 7. Theapparatus of claim 5 wherein panel mounting means provides a triangulartop enclosure,

said lamps being disposed in a triangular arrangement corresponding tosaid triangular top enclosure.

References Cited UNITED STATES PATENTS 2,434,450 l/ 1948 Williford 731502,804,770 9/1957 Gunther et al. 73150 3,292,418 12/ 1966 Oehme et a173150 X OTHER REFERENCES Circular No. 334, Painting Tests on PanelsImpregnated With Zinc Chloride or Creosote, H. A. Gardner, June 1928,pp. 588-598.

Brochure, AtlasElectric Devices Co., Fade-Ometers and Weather-Ometers,1962, pp. 4, 5, 12, 13, 16-25.

LOUIS R. PRINCE, Primary Examiner H. C. POST I11, Assistant Examiner

